Horticultural lighting systems are used to provide artificial light for growing plants within indoor environments. A conventional lighting arrangement includes a single high intensity discharge (HID) high pressure sodium lamp (HPS) which is used to cover five by five squared feet of area. These lamps can be arranged to cover adjacent regions of approximately the same square area. A goal in these lighting systems is to achieve uniform light distribution, and in particular uniform photosynthetically active photon density in the grow area. A single light source produces a photonic density pattern as expected; a high peak photonic density directly under the lamp with a sharp drop off moving outward from that point. This problem increases dramatically with height, moving upward toward the lamp. Some have attempted to solve this secondary problem with moveable lamps that can be raised as the plants grow, which increases the complexity of the lighting system.
To address the photonic density variation issue, the conventional approach has been to add light elements to fill the area over the grow area with light elements. This approach has been enabled by light emitting diode (LED) technology, which allows small light emitting elements to be arranged in a matrix in a panel format over the growing area. However, while filling the overhead area with light emitting elements has produced some improvement in light uniformity in the grow area under the light panel, testing shows that these arrangements still result in a non-uniform photon distribution, with the center of the footprint (squared area) receiving the highest photonic density, which decreases in density with increasing distance from the center, under the light source.
As a result, with both single point light source fixtures, and panel fixtures, plants along the perimeter of the footprint receive less light, and growth is not uniform. Furthermore, the heat generated by these lamps can damage plants, and adjusting the height to a level that ensures damage will not occur exacerbates the non-uniformity of the light. Also, with single bulb systems where there is only one bulb with HID/HPS, spectral customization is limited to the kelvin temperature and color rendering index of that single bulb. Many have attempted to remedy this problem by using lower intensity LEDs, spread across smaller fixtures, in a matrix. All of which still result in a substantial lack of uniformity of photonic density across the growing area under the light fixture.
Therefore, a need exists to overcome the problems with the prior art as discussed above.